Many ball games either require or are enhanced by devices which restrict the movement of the ball. For example, most baseball playing fields include a backstop located behind home plate consisting of a vertical screen, commonly extending toward first and third base for some distance, and often with an overhead roof component. The purpose is to prevent the ball from leaving the immediate area of play when thrown or struck into the backstop. The result is one of both utility and safety since spectators may locate behind the backstop for protection. In most instances these barriers are permanent structures consisting of steel chain link or wire screens supported by steel or wood frames. Although this type of construction is generally durable, it is also relatively expensive. Furthermore, the barrier normally must be utilized where originally built since relocation is difficult. The fields on which they are constructed often may not be utilized for other sports or activities due to the physical restrictions which they impose. For example, permanent baseball backstops can impede the seasonal use of otherwise large open areas for soccer or football. Semi-portable devices are known, such as backstops and cages with wheels attached thereto. Other relatively small devices have been built without permanent attachment to the ground to allow for manual relocation. U.S. Pat. No. 4,072,295 to Roberts (1976) discloses a foldable, transportable backstop. However, the ease and speed of relocation of such existing devices is arguable.
The practice of many ball games is also aided by the use of projectile arresting devices. Baseball pitchers can practice without a catcher by throwing balls into a backstop or screen. Similarly, a batter may hit balls off a tee into such devices. Pitchers and batters often practice together in a cage-like enclosure which restricts the flight of the ball to a predetermined limited area. Many such practice devices are at least semi-portable. The most common construction consists of netting suspended between rigid support posts or frames which are in turn often stabilized by tension guys to the ground plane. As an example, U.S. Pat. No. 3,593,997 to Boehner (1971) discloses a batting cage of this type of construction. In actual use this type of construction imposes several disadvantages. Balls may strike the rigid material resulting in damage over the long term. The rigid materials can also cause high energy rebounding of the ball resulting in a safety hazard or other undesirable performance characteristics. High energy rebounding can also be caused by the tautness of the screen or its supporting ropes or cords. Such construction can be difficult to assemble and adjust to the desired shape. Also, these structures can tend to lose shape and stability with use. U.S. Pat. No. 4,127,267 to Bay and DiMarco (1977) discloses a device with improved energy absorbing capability over previous devices. This is accomplished by removing rigid materials from the path of the projectiles and by hanging the netting relatively loosely from its supporting frame. This device also returns to its proper shape by gravity after impact by the projectile. These improvements, however, are the result of a collapsible support which is relatively complicated, heavy, and expensive to manufacture.
The primary disadvantages of currently known projectile arresting devices utilized as screens, backstops, nets, and cages for the purpose of restricting the flight of a game ball during the playing or practicing of sports such as baseball, soccer, golf and tennis are summarized as follows:
1. They are often permanent structures which are difficult to relocate and expensive to construct. PA0 2. Portable devices are often heavy and otherwise difficult to assemble and transport. PA0 3. Many devices tend to loose their shape and stability after use. PA0 4. Rigid elements are subject to damage when struck by projectiles. PA0 5. Rigid elements tend to reflect projectiles without dissipating kinetic energy leading to potentially unsafe operating conditions. PA0 6. Taut screens and highly tensioned support ropes and cords tend to reflect projectiles without dissipating kinetic energy leading to potentially unsafe operating conditions. PA0 7. Devices which address some of the previously mentioned disadvantages are expensive to manufacture. PA0 1. All rigid materials are located outside of the potential path of the projectiles. PA0 2. The barrier which arrests the flight of the projectiles is completely flexible. PA0 3. The potential for high energy rebound of the projectile is minimized. PA0 4. The kinetic energy of the projectile is absorbed and dissipated safely by the response of the device to the impact of the projectile. PA0 5. The device retains its original shape after repeated use. PA0 6. Assembly and disassembly of the device is easy and does not require skilled labor, special tools, or equipment. PA0 7. The device can quickly and easily relocated. PA0 8. The materials of construction for the device may be extremely light in weight. PA0 9. The materials of construction are commonly available; the manufacture does not require skilled labor nor sophisticated equipment or processes; and, consequently, the device is very inexpensive.